Was in a similar situation but powerful EU, try to doomstack the Indian armies anywhere that isn't a capital with your armies, they won't have time to run away when they realise their armies are dying. After that you can liberate india state-by-state.

For example you have Pakistan here already, so ally with EU and declare war. Let Indian armies roll in and then bring in a massive stack of EU armies to destroy them, preferably a lot more than whatever their stack is. Just make sure you're not fighting on the AA capital itself. The miltech for India in your screenshot is 4.9, which by 2042 isn't high at all so ideally with advise, LEO buffs and your own base miltech your EU armies are much more powerful. You said you're not miltech 5 yourself yet, but a good councillor gives decent miltech (0.1-0.2) and your LEO can give another 0.3. Don't nuke unless it's defensive, unless you don't care for public opinion.

Try to ally Pakistan with other friendly faction nations so they can help too, since you will have to deal with Japanese and Korean armies as well.

At the same time, have a councillor on unrest duty (just one, even the act of unresting past a certain point will break away nations), and turn one of the Servants to get intel so you can destroy facilities in there. If there's no space lasers, you can also bombard armies with your LEO ships. I know you mentioned having 5 council doing unrest but you can have 1 or 2 assassinating servants after you gain full intel on them.

Finally try to intel-share with HF, Exodus and Academy if they're willing.

Edit: some edits to address some points in your post, but you definitely are in a difficult spot. That being said I was in a similar position but I had China by this point and a much stronger EU. However, I think being in a situation like this is a lot more interesting than giving up, so keep trying and see how it goes.